Adhesive lacquer



Patented Jan. 6, 1942 UNITED STATES TENT OFFi Jung, Dessau,

Germany, assignors, by mesne assignments, to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application May 24, 1938, Serial No. 209,722. In Germany June 5, 1937 (on. zoo-17) 1 Claim.

of film, there generally persists after the joining of the component layers a tendency of the combined foil to curl which is due to the different shrinkage of the component layers. In photographic processes in which, for example, photographic pictures are produced in cellulose hydrate foils which are then placed in one or more layers on a diffusely reflecting base to 'produce pictures to be viewed by reflected light there is the danger in using the adhesive hitherto customary that the finished picture will curl strongly. If for example the films are stuck on the paper in the wet condition, for example by a gelatin solution, there are obtained, owing to the fact that the cellulose hydrate foils adhere as they dry, strongly curling pictures which are useless.

It is known to stick dry cellulose hydrate films on paper with the aid of lacquers with which the paper or film is previously coated. Such lacquers have, however, proved to be-unsatisfactory for this purpose. If the wet cellulose hydrate foil containing the photographic pictures is first dried in order to stick it on paper it is only possible to obtain smooth, faultless adhesive films if they are dried while being squeegeed on a planebase such as glass or Celluloid. This, however, produces dry films which are the same size as they were when wet; they are therefore in tension and tend to shrink slowly to the size natural in the dry condition. This process is only gradual and occupies some days or weeks. If the film were stuck on the paper with the lacquer referred to above immediately after drying, curling pictures would likewise be obtained. On the other hand it is not possible in practice to wait until the shrinking has ended. An attempt has been made to overcome this disadvantage by sticking the picture on thick paper or by backing the paper with a foil of cellulose hydrate; in both cases pictures are obtained which are unsatisfactory on account of their stiffness and other objectionable properties.

It is an object of our invention to provide mixtures of certain substances which when dissolved in suitable solvents have the novel property that while they stick the cellulose hydrate film on paper with a powerful bond which can scarcely be loosened without special agents. they yet leave 55 Further objects of our invention will appear from the specification following hereinafter.

If cellulose hydrate dried under stress is stuck on paper with a lacquer composed in accordance with the invention there is obtained a completely plane picture which is easily flexible in every direction. The picture fully maintains these properties in spite of the fact that after some days or weeks the foil has become visibly smaller. With large formats this shrinkage may amount to V cm. or more (recognizable at the white edges produced) without alteration of the plane configuration or elasticity of the picture.

We have found that such a lacquer solution must consist mainly of a solution in a suitable solvent of at least one representative of each of three groups of substances characterized respectively by definite properties. These groups of substances are as follows:

l. Film-forming substances,

2. Substances forming elastic plastic masses,

3. Substances being water-soluble or capable of swelling in water and soluble in organic solvents.

The solvent may advantageously consist of a 5 mixture of at least one water-insoluble and one water-soluble substance.

Examples of substances in the aforesaid groups are as follows:

l. Acetyl cellulose, nitrocellulose, ethyl cellulose,

2. Polyvinyl esters which include the polyacrylic acid esters,

3. Glycerol triphthalate, mixed polymers formed from polyvinyl esters or ethers and maleic' acid anhvdrlde.

40 For the production of a lacquer embodying the aforesaid properties a mixture of one substance from each of the groups 1-3 suflices.

The following examples serve to illustrate the invention but they are not intended to limit it thereto.

The paper or the like serving as base or the cellulose hydrate containing the photograph is coated or sprinkled with the lacquer described below. This is best left to dry for a short time, whereupon the dry, cold or warm cellulose hydrate foil is rolled upon the base. The lacquer has the additional advantage that the foil is caused to adhere in the cold and without any special auxiliary agents merely by an ordinary roller squeegee.

The addition of a solvent of high boiling point or a substance which softens in the heat causes may be used. Thus for example a number of component pictures of a three-color picture con:

tained in transparent films which have been joined together in the wetwith a gelatin solution can be dried in the aforesaid manner and then stuck on paper with the lacquer claimed.

Lacquers which can be used according to the invention are for example composed as follows: 0

' Grams Polyvinyl acetate of high viscosity 82 Glycerol phthalic acid resin 82 Ethyl cellulose 01 low viscosity 5 Soft glycerol triphthalate '75 Triacetin 20 Tricresyl phosphate 26 Acet0ne 430 Methanol 50 Benzene 230 Grams Polyacrylic acid methyl ester 52 Nitro-tllm waste 14 Glycerol triphthalate or the same quantity or a mixed polymer formed from polyvinyl An adhesive lacquer comprising an organic solution of a celluloslc film-forming substance. a resinous elastic plastic polyvinyl ester and a substance which is at least swellable in water and soluble in organic solvents, selected from the class consisting of mixed polymers from polyvinyl esters and maleic acid anhydride and mixed polymers of polyvinyl ethers and maleic acid anhydride.

JOHN EGGERT. BRUNO WENDT, ADOLF JUNG. 

